Error controlling algorithms may be largely classified into two types: an automatic repeat request (ARQ) method and a forward error correction (FEC) method.
The ARQ is accomplished by a data link protocol of an OSI model and the FEC is accomplished by a physical layer. In the ARQ, the terminal has an error-detecting function for detecting errors in a message to request a retransmission when a transmission line is a half-duplex or a full-duplex line. In the FEC, the terminal has an error-correcting function for detecting errors in a message to correct the errors without requesting a retransmission. The ARQ has been widely used in data communication networks since it has a more simple structure and a higher reliability of data than the FEC. However, as the bit error rate of the channel is increased, the throughput of information is rapidly decreased in the ARQ. Meanwhile, in the FEC, the throughput of information is preserved at a predetermined level regardless of the bit error rate of the channel, but high reliability cannot be easily achieved.
In order to compensate for these drawbacks, a hybrid ARQ scheme (hereinafter, called HARQ) combining the ARQ and the FEC has been introduced. The HARQ scheme can have throughput of information similar to that of the FEC and reliability similar to that of the ARQ. In the HARQ, error-detecting and retransmission are requested after predetermined error-correction has been attempted by the FEC. Accordingly, since the conventional ARQ and FEC are combined, the HARQ may have a higher reliability and a lower error rate than the ARQ or FEC.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.